CH. XXl] OSMUND ACEAE 325 



Osmundaceae, but there is no adequate reason for referring 

 them to this family. 



The generic name Pteridotheca is employed by Scott as a 

 convenient designation for unassigned petrified sporangia of 

 Palaeozoic age with an annulus and other characters indicating 

 fern-affinity. In the species P. Butterworthi^ the sporangia are 

 characterised by a group of large cells suggesting comparison 

 with the annulus, or what represents the annulus, in Osmun- 

 daceae and Marattiaceae. Scott has also described a spor- 

 angium from the Coal-Measures containing germinating spores^ ; 

 the structure is similar to that of recent Osmundaceous sporangia, 

 and it is interesting to note that germinating spores have been 

 observed in the recent species Todea hymenophylloides^- 



Additional evidence of the same kind is afforded by fertile 

 specimens of a quadripinnate fern with deeply dissected oval- 

 lanceolate pinnules described by Zeiller firom the Coal-Measures 

 of Heraclea in Asia Minor as Kidstonia heracleensis * (fig. 

 256, E). Carbonised sporangia were found at the base of 

 narrow lobes of the ultimate segments and, as seen in fig. 

 256, E, the sporangial wall is distinguished by a plate of larger 

 cells occupying a position like that of the " annulus " of recent 

 Osmundaceae. Zeiller regards the sporangia as intermediate 

 between those of Osmundaceae and Schizaeaceae. From the 

 same locality Zeiller describes another frond bearing somewhat 

 similar sporangia as Sphenopteris (Discopteris) Rallii (fig. 

 256, D)°: the term Discopteris was instituted by Stur for 

 fertile fronds referred by him to the Marattiaceae'. 



It is by no means safe to assume that these and such Upper 

 Carboniferous sporangia as Bower^ compared with those of 

 Todea were borne on plants possessing the anatomical characters 

 of Osmundaceae rather than those of the extinct Palaeozoic 

 family Botryopterideae. This brings us to the important fact, 

 first pointed out by Renault, that the Botryopterideae are 

 essentially generalised ferns exhibiting many points of contact 

 with the Osmundaceae'. It is clear that whether or not we 



1 Scott, D. H. (08) p. 292. ^ Scott (04) p. 18. 



3 Boodle (00) p. 484. * Zeiller (99) PI. n. figs. 5, 6. 



6 Ihid. PI. II. fig. 10. * See p. 402. 



' Bower (91) PI. vii. ' Scott, D. H, (09). 



